The successful immunotherapy of cancer will depend upon understanding the complex relationships between immune cells and their tumor targets. Neutrophils are key participants in antibody-dependent host resistance to cancer whereas T cells are crucial in antibody-independent anti-tumor mechanisms. However, the nature of transmembrane signaling in response to antigens and the chemical communication between effectors and targets remain poorly understood. This NCI program has established the technique of high speed microscopy, which is unique to this laboratory; by using very brief shutter speeds, chemical signals within cells do not have enough time to move, which thereby retains a great deal of spatiotemporal information. Strikingly, these studies have revealed the routes chemical signals follow within and among cells, thus providing a completely new way of studying signal transduction. We will now exploit this new tool to study the interactions among immune and tumor cells in unprecedented detail. We will determine how chemical information, such as calcium and oxidant waves, travel among neutrophils and antibody-opsonized targets, including multi-cellular tumor spheroids. In particular, we will address how rapid signals travel among two or more cells and how these events lead to tumor cell apoptosis using biophysical, biochemical and computational tools. Preliminary studies have revealed at least four calcium waves associated with cytotoxic T lymphocyte (CTL)-mediated tumor cell killing. These signals will be systematically dissected using biochemical, biophysical, and genetic tools. In particular, we will explore the dynamic mechanism of signal processing by T cells. For example, we will explore how different peptide antigens bound to MHC class I molecules elicit different signals and functions in CTLs. The mechanism of CTL-induced tumor cell death will be studied, including the potential role of perforin in aberrant calcium signaling in tumor cells. By using a confluence of new imaging, computational, and immune cell tools, our studies will reveal and characterize mechanisms of leukocyte-mediated tumor cell destruction at a novel level of cellular complexity. These new insights are likely to lead to advances in immunotherapy of cancer.